1. FIELD OF THE INVENTION
The invention relates to a hub shell, more particularly to a bicycle hub shell which comprises two separate pieces and which can bear the presence of a high twisting force applied thereto.
2. DESCRIPTION OF THE RELATED ART
FIG. 1 shows a bicycle hub unit with a conventional bicycle hub shell 1. The conventional bicycle hub shell 1 is a tubular body la which confines an axial bore therethrough and which has a pair of annular mounting flanges 1e that protrude respectively and radially from two axial end portions 1c (refer to FIG. 2) of the tubular body 1a for connection with a plurality of spokes (not shown). Since it is difficult to form the bicycle hub shell 1 as a one-piece body, the conventional hub shell 1 is divided into three separate parts, namely the tubular body 1a and a pair of spoke mounting units 1E with the mounting flanges 1e. As illustrated in FIG. 2, the axial end portions 1c of the tubular body 1a are connected to the spoke-mounting units 1E by means of the radially and outwardly expanding axial end portions 1c.
A drawback of the conventional hub shell 1 is that when the conventional hub shell 1 is in use, a twisting force is generated by the spokes (spokes) connected to the spoke-mounting units 1E due to friction between the wheel (not shown) and the ground. The twisting force concentrates near the connecting position 1d such that the force is easily transferred to the connecting position 1d. Since the generated twisting force is opposite to an applied force via the shaft 2 and since the spoke-mounting units 1E are not formed integrally with the tubular body 1a, the tubular body 1a may disengage untimely from the spoke-mounting units 1E and thus rotate idly in the event that the generated twisting force exceeds the bearable capacity.